1. Field
The present disclosure relates to a brake actuating apparatus, and more particularly, to a brake actuating apparatus using an electric motor.
2. Discussion on Related Technology
A typical hydraulic braking apparatus comprises a hydraulic circuit, wherein pedal pressure generated through depression of a pedal by a driver is increased in a master cylinder and a booster and then transmitted through hydraulic tubing to a braking apparatus mounted to each of road wheels. The hydraulic brake has disadvantages in that it is impossible to perform braking if the hydraulic tubing is damaged, it takes a great deal of time to transmit a pedal operation signal for braking to the brake through the hydraulic tubing, resulting in poor responsiveness, and a plurality of parts including the hydraulic tubing are required, resulting in the increased weight of a vehicle.
Recently, there has been proposed a braking apparatus, wherein instead of such a complicated hydraulic circuit, a motion converting means such as a ball screw is used for converting a rotational motion from a motor to a linear motion so as to urge a brake pad, thereby performing the braking function. Such a type of braking apparatus is called “brake-by-wire” type and has an advantage of easy control. As for the “brake-by-wire” type braking apparatus, however, a relatively large-sized motor, a reducer and a means for converting a rotational force of the motor into a liner motion are inevitably required in order to obtain an appropriate braking force. Moreover, the braking apparatus may further have a clutch used for controlling transmission and interruption of the power from the motor in order to improve the responsiveness of the brake, which causes disadvantages of increase in the volume of the apparatus, difficulty in manufacturing the apparatus, and increased costs. Particularly, the apparatus has a drawback in that mechanical braking cannot be performed if an unexpected electrical failure or defect is produced in the apparatus.
As a braking apparatus for solving the problems in the hydraulic braking apparatus and the “brake-by-wire” type braking apparatus, there has been proposed an apparatus that employs a hybrid braking system using both a motor and hydraulic pressure. U.S. Pat. No. 5,348,123 entitled “Brake Actuating Apparatus for a Vehicle” discloses the technical constitution of a braking apparatus that controls the pressure of a fluid in a cylinder for urging a brake pad, using a motor. As shown in FIG. 16, the patent discloses a brake system in which a rotational motion from a motor 3 is converted into a linear motion by means of a ball screw 5 and then transmitted to a driving piston 7 and the advance of the driving piston 7 causes a working fluid 1 to urge a pressing piston 9 so that the pressing piston can be moved forward, thereby performing braking.
However, the brake actuating apparatus disclosed in the U.S. Patent should inevitably have a motion converting means such as a ball screw in order to convert the rotational motion from the motor to the linear motion. Further, the brake actuating apparatus should be additionally provided with a structure for securely returning the member, which has been moved forward through the conversion of the rotational motion into the linear motion by the motion converting means, after braking. Accordingly, there are disadvantages in that the structure of the apparatus is complicated, it is difficult to manufacture and assemble the apparatus, and production costs increase.
The discussion in this section is to provide general background information, and does not constitute an admission of prior art.